Science in the Classroom is a collection of annotated research papers and accompanying teaching materials designed to help students understand the structure and workings of professional scientific research.

Black Holes

What You Need

Purpose

To introduce black holes and demonstrate how space telescopes can provide data to support current hypotheses.

Context

In this activity, students will explore a Web resource called No Escape: The Truth About Black Holes on the Amazing Space website. This is a module that introduces students to the science of black holes. Students examine the anatomy of a black hole using a diagram of an accretion disk, the event horizon, and jets of hot gas. This module also includes subsections about myths, the history related to the discovery of black holes, an animated trip to the center of a black hole, a discussion of different types of black holes, and an opportunity to see actual Hubble images that support the hypothesis of black holes.

Planning Ahead

You should read the Teacher Page, paying particular attention to student misconceptions and prerequisites.

You may also refer to Science Background to refresh your understanding of black holes. The Black Holes teacher sheet contains a list of vocabulary words that students will encounter in the module. You may wish to go over this list with the class since the science of black holes uses terminology that is likely not familiar to most students. However, do not expect students to master the vocabulary before they work on the module. Merely point out the words to them and explain to them that when they encounter these words in the activity, they can click on them to view a definition.

Motivation

Ask students: “What is a black hole?” Encourage a brief discussion in which students can freely propose ideas about their conceptions of black holes. Use these ideas to construct a definition of a black hole based on class consensus. Write it on the chalkboard for future reference. Then refer students to the Black Holes Exploration student esheet, which will direct them to Gravity Betrays Black Heart of Milky Way.

Once students have had a chance to read this article, refer them to your class definition of a black hole and allow students time to revise it. Ask, "Are there still some things about a black hole that you don’t understand?" Make a list of these things.

There is quite a bit of specialized vocabulary surrounding the science of black holes. So that students can have a better understanding of these terms when they encounter them, you may wish to review the vocabulary found in the Black Holes teacher sheet. One way to approach this is to provide students with a list of the terms that they might encounter and explain to them that these terms will be underlined in the module. They can click on them to look at definitions as they explore the resource. If you think it will be helpful to your students, you can ask them to jot down these definitions as they go along. However, make sure to emphasize that the point of the lesson is to understand what a black hole is and that simply being able to define new vocabulary is not the same as understanding the process of how black holes are formed. The student sheet will ask them to explain in their own words some of the key concepts embodied in this vocabulary.

After students have completed the module, conduct a complete discussion of the ideas covered in the student sheet. Then, refer back to the original class definition of a black hole and allow students to refine it based on their deeper understanding. It is important that students be able to discuss the reasons why they have refined their understanding and not merely substitute one definition for another.

Assessment

The following questions can be used to assess student understanding about black holes:

What does a black hole look like?

(A black hole itself is invisible because no light can escape from it.)

Are there any pictures of a black hole? If not, why not?

(There are no "real" pictures of a black hole. This is because black holes themselves do not emit or reflect any light [that's why they are called black holes], and they are too small and too far away to be imaged. There are images of binary star systems consisting of one normal star and one black hole, and of the central regions of galaxies that are believed to contain black holes. Scientists need to study the motion of stars to infer that there must be a black hole.)

Could a black hole suck up all the matter in the universe? Why? Why not?

(A black hole has a "horizon," which means a region from which you can't escape. If you cross the horizon, you're doomed to eventually hit the singularity. But as long as you stay outside of the horizon, you can avoid getting sucked in. In fact, to someone well outside of the horizon, the gravitational field surrounding a black hole is no different from the field surrounding any other object of the same mass. In other words, a one-solar-mass black hole is no better than any other one-solar-mass object [such as, for example, the sun] at "sucking in" distant objects. )

You can also use the activity “Beats Us, You Explain” also found on the No Escape: The Truth About Black Holes module as an assessment. In it, students are asked to explain the concept of a black hole to a targeted audience in 200 words or fewer. Images are provided for students to use as illustrations for their descriptions. Student work should demonstrate an understanding that the formation of black holes is part of the process of star formation and destruction and that technology has enabled us to understand more about this process as advanced telescopes help to provide evidence about the existence of black holes.

Extensions

Black Holes contains a discussion of some of the popular myths about black holes that have been perpetuated by fictional depictions of black holes.